Getting started with the ocs tool

The compilation of Opal sources is driven by a single, batch-oriented command ocs, which is similar to the traditional Unix tool make.

For example, we compile the mandatory hello-world program with ocs as follows: 

    $ cd examples/HelloWorld
    examples/HelloWorld $ ocs
->  Generating rules for hello'HelloWorld ...
->  Checking Signature of HelloWorld ...
->  Compiling Implementation of HelloWorld ...
->  Generating  object code for HelloWorld ...
->  Generating startup code for hello ...
->  Linking hello ...
    examples/HelloWorld $ ./hello
->  Hello World!
Like make, ocs is ``lazy'' and performs only the steps necessary to bring its target up to date. Thus, calling ocs again yields: 
    examples/HelloWorld $ ocs
->  Nothing to be done for `all'.
Only if sources change (reflected by their time stamps) will (partial) recompilation be carried out: 
    examples/HelloWorld $ touch HelloWorld.impl
    examples/HelloWorld $ ocs
->  Generating rules for hello'HelloWorld ...
->  Compiling Implementation of HelloWorld ...
->  Generating  object code for HelloWorld ...
->  Generating startup code for hello ...
->  Linking hello ...
ocs places intermediate compilation results in a subdirectory called OCS. In order to enforce recompilation, or to recover disk space, simply remove this directory: 
    examples/HelloWorld $ rm -rf OCS
    examples/HelloWorld $ ocs
->  Generating rules for hello'HelloWorld ...
    ...
->  Linking hello ...
Sometimes ocs gets confused by changes on the SysDefs file - for example, if structures have been renamed. If the operation of ocs fails for such reasons, removing ./OCS helps.
ocs gets its information from a file called SysDefs (like make from Makefile) in the current directory. For the hello-world program, this file has the following contents: 
    examples/HelloWorld $ cat SysDefs
->  TOPSTRUCT = HelloWorld
->  TOPCOM = hello
A SysDefs file contains a set of variable definitions in a make-like syntax. For hello-world, we only had to define the following variables: TOPSTRUCT, the name of the structure which contains the top-level monadic command, and TOPCOM, the name of this command.

Remark: by running "ocs -top HelloWorld hello", a file SysDefs.HelloWorld-hello will be created which can be renamed SysDefs.
A SysDefs file may contain further variable definitions, and ocs runs in a variety of modes supporting diverse options. For further documentation, see the ocs(1) manual page.

The operation of ocs may be further customized by a project definitions file. If the environment variable OCSPROJECT is defined, it must point to a file which contains the project definitions. See examples/Customize for examples of project definitions files.

The Opal Group
Last modified: Tue Nov 25 16:04:12 1997